The invention relates to optical disc apparatus, and in particular, to a system for writing or reading out information stored in optical disc medium.
Optical disc technology is currently gaining increasing importance in the field of information storage. This increasing interest is primarily due to the fact that optical discs are capable of far greater storage capacity than standard magnetic discs now used for computer memory, while the reading apparatus and recording medium are typically much less expensive.
Usually, the optical disc includes one or more layers of suitable materials (such as Te-Se) in which pits are formed. The length of a pit, as well as the presence or absence of a pit, can represent the stored information. The pits are formed in several tracks along the disc in a manner similar to a phonograph record. In order to read-out the information, a laser beam is focused into the desired track by optical components included in a head which is moved in a radial direction while the disc is rotated. The light which is reflected by the disc medium is directed to one or more photodetectors which give an electrical signal indicative of the presence or absence of pits along the track (as well as their shape) and so the recorded information may be reproduced.
One of the disadvantages of optical disc over magnetic disc technology at the present time is the slower access time capability in the former. The usefulness of optical discs in future systems will increase if faster access times are available.
Consequently, it is a primary object of the invention to reduce access times in optical disc apparatus.